As a synthesis process for a quaternary salt such as, for example, a quaternary ammonium salt, a process of quaternarizing a tertiary amine with an alkyl halide or a dialkylsulfuric acid under heating has been employed.
For example, when an alky halide is used as a quaternarization reagent, the quaternarization reaction is shown by the following equation: EQU R.sub.3 N+R'X.fwdarw.R.sub.3 R'N.sup..sym. X.sup..crclbar. (X: halogen)
Further, in the case of producing quaternary ammonium salts having various different anions, anion exchange of quaternary ammonium halides (e.g., chlorides, bromides, and iodides) have been usually employed.
In the case of an anion exchange reaction of a quaternary ammonium halide, a process, in equilibrium, shown in the following equation is known: EQU R.sub.3 R'N.sup..sym. X.sup..crclbar. +H.sup..sym. A.sup..crclbar. .revreaction.R.sub.3 R'N.sup..sym. A.sup..crclbar. +H.sup..sym. X.sup..crclbar.
wherein A.sup..crclbar. is an anion being exchanged.
When H.sup..sym. A.sup..crclbar. being exchanged is a strong acid, the equilibrium is deviated to the right side of the aforesaid equation and hence the desired anion exchange reaction can be sufficiently progressed, but, when H.sup..sym. A.sup..crclbar. is a weak acid such as an organic acid, it is very difficult to perform the anion exchange reaction to be completed.
As other process, a process of reacting a quaternary ammonium halide with an alkali metal salt or an alkaline earth metal salt and a process of reacting a quaternary ammonium halide with a silver salt may be considered. However, in these processes, it is considerably difficult to completely remove raw material anions from the desired quaternary ammonium salt thus obtained, and hence, these processes are unsuitable to produce a quaternary ammonium salt of high purity. And, the process of using a silver salt is expensive and hence unsuitable as an industrial process.
From the aforesaid view points, as a process for producing a quaternary ammonium salt of high purity, a process of once converting a quaternary ammonium halide into a quaternary ammonium hydroxide (Reaction a), and then, neutralizing the hydroxide with an acid corresponding to the anion of the desired salt (Reaction b) as shown in the following equation is most general: EQU R.sub.3 R'N.sup..sym. X.sup..crclbar. .fwdarw.R.sub.3 R'N.sup..sym. OH.sup..crclbar. (Reaction a) EQU R.sub.3 R'N.sup..sym. OH.sup..crclbar. +H.sup..sym. A.sup..crclbar. .fwdarw.R.sub.3 R'N.sup..sym. A.sup..crclbar. +H.sub.2 O (Reaction b)
As the process for producing quaternary ammonium hydroxide by aforesaid Reaction a, various processes are known such as; for example, in the case of using a bromide, are known reacting a quaternary ammonium bromide dissolved in a suitable solvent with a quaternary ammonium hydroxide type ion exchange resin, reacting a quaternary ammonium bromide with an alkali metal oxide in a liquid medium, separating bromide ions as Br.sub.2 by an electrochemical method to provide the hydroxide, and using a silver compound.
However, these processes are all expensive as an industrial process and, in particular, in the case of producing a high-pure product wherein the content of halide in the quaternary ammonium hydroxide is controlled to an order of ppm, the production cost becomes considerably high.
The aforesaid matters are same in the case of producing quaternary phosphonium salts. That is, as a process of synthesizing a quaternary phosphonium salt, quaternarizing a tertiary phosphine with an alkyl halide, a dialkylsulfuric acid, etc., under heating as shown in the equation: EQU R.sub.3 P+R'X.fwdarw.R.sub.3 R'P.sup..sym. X.sup..crclbar. (X: halogen)
and then performing, in equilibrium, an anion exchange by the reaction shown in the following equation is generally known: EQU R.sub.3 R'P.sup..sym. X.sup..crclbar. +H.sup..sym. A.sup..crclbar. .revreaction.R.sub.3 R'P.sup..sym. A.sup..crclbar. +H.sup..sym. X.sup..crclbar.
Also, as a process for producing a high pure quaternary phosphonium salt, a process of once converting a quaternary phosphonium halide into a quaternary phosphonium hydroxide (Reaction a') and then neutralizing the hydroxide with an acid corresponding to the anion of the desired salt (Reaction b') as shown in the following equations is most general: EQU R.sub.3 R'P.sup..sym. X.sup..crclbar. --R.sub.3 R'P.sup..sym. OH.sup..crclbar. (Reaction a') EQU R.sub.3 R'P.sup..sym. OH.sup..crclbar. +H.sup..sym. A.sup..crclbar. --R.sub.3 R'P.sup..sym. A.sup..crclbar. +H.sub.2 O (Reaction b')
Furthermore, the processes for producing the quaternary phosphonium hydroxide by aforesaid Reaction a' are expensive as an industrial process same as in the aforesaid cases of producing a quaternary ammonium hydroxide and, in particular, in the case of producing a high-pure product wherein the halide content in the quaternary phosphonium hydroxide is controlled to an order of ppm, the production cost also becomes considerably high.